The Canadian

Centre for Environmental Modelling and Chemistry

AirWater Model

Version 2.00 - November 2004

New in version 2.00!

Software Description

The AirWater model calculates the air-water exchange characteristics of a chemical based on its physical chemical properties and total air and water concentrations. The distribution of the chemical at defined, probably unsteady-state, conditions is described. Since the system may not have acheived steady-state concentrations, for comparison, the fugacity in each medium is calculated from the other medium, assuming steady-state conditions.

This model is useful for estimating rates of chemical loss from treatment lagoons, ponds, and lakes, for estimating deposition rates of atmospheric contaminants, and for interpreting observed air and water concentrations to establish the direction and rate of transfer. The results of changes in chemical and environmental properties may be explored by modifying the input data. Incremental changes in input properties can be used to obtain a sensitivity analysis.

Features of the AirWater Model:
Provides a database of chemicals and chemical properties.
Permits temporary additions/changes of chemicals and their properties to a simulation.
Permits permanent additions, changes and deletions of chemicals and their properties to the database.
Provides a database of environments and environmental properties.
Permits temporary additions/changes of environments and their properties to a simulation.
Permits permanent additions, changes and deletions of environments and their properties to the database.
Provides context-sensitive Help.
Displays and prints the AirWater model calculations, as performed by the program.
Allows the printing of simulation tables and the summary diagram.
Allows the program results to be saved as text file viewable by standard spreadsheet software.

This program was based on the following publications:

Mackay, D., Paterson, S., Schroeder, W.H. 1986. Model Describing the Rates of Transfer Processes of Organic Chemicals Between Atmosphere and Water. Environ. Sci. Technol. 20: 810-816.

Mackay, D. 2001. "Multimedia Environmental Models: The Fugacity Approach - Second Edition", Lewis Publishers, Boca Raton, pp. 191-194.

The required input data are:

Chemical Properties:

  • chemical name
  • molar mass
  • data temperature
  • water solubility
  • vapor pressure
  • log Kow
  • melting point
  • Environmental Properties:

  • area
  • water depth and air height
  • densities for the suspended particles and for aerosols
  • organic carbon content of the suspended particles
  • concentrations of the particles
  • transport velocities
  • water side air-water mass transfer coefficient
  • air side air-water mass transfer coefficient
  • aerosol dry deposition velocity
  • rain rate
  • aerosol scavenging coefficient


  • chemical concentrations in air and water

    Model Output:

  • all input data
  • chemical amounts in each medium
  • residence times in each medium
  • fugacity of each medium for the user-specified concentrations
  • fugacities at steady-state
  • intermedia transport and loss rates and D values
  • Z values and concentrations in all subcompartments
  • a summary diagram

    Minimum system requirements are an IBM-compatible PC running Windows 98 or XP. This model will not run under Windows NT or 2000.

    For non-Windows users the BASIC, Airwater model is available.

    Please read the AirWater SOFTWARE LICENSE before downloading the software. Use of the software constitutes your agreement to abide by the terms and conditions set out in the license agreement.


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    Last updated June 10, 2013.